1. Field of the Invention
This invention relates generally to helicopters and more particularly to a method of converting an existing helicopter airframe to a special purpose use such as, for example, a gunship or a firefighter and a helicopter constructed thereby.
2. Discussion of the Prior Art
Several special purpose helicopters have been developed. One such special purpose helicopter is disclosed in U.S. Pat. No. 3,327,969 to Head which discloses a helicopter which is adapted for in-flight conversion from a helicopter type of flight to a conventional airplane type of flight and vice versa.
U.S. Pat. No. 3,902,688 to Seibel et al discloses a helicopter converted to a gunship wherein a pair of horizontal stabilizers are mounted on a vertical stabilizer as to be outside the fuselage wake in forward flight. The vertical distance between the tips of the vertical stabilizer is made sufficient to keep one horizontal stabilizer out of the high downwash region behind the fuselage at all angles of attack. A large horizontal stabilizer is mounted high enough above the tail boom to be outside the high velocity main rotor wake. The ratio of the areas of the upper and lower horizontal stabilizers is 70:30 for optimum pitch moment characteristics.
U.S. Pat. No. 3,921,938 to Jupe et al discloses a helicopter converted to fit into a small storage area such as on a ship. The main rotor blades are foldable forwardly to a stowed position above a forward part of the fuselage and the tail boom from a longitudinal center line of the fuselage and foldable forwardly to a stowed position along one side of the fuselage to significantly reduce the folded dimensions of the helicopter over existing configurations, which is a very important criterion when the helicopter has to be stowed in a confined space such as a ship's hangar. The fuselage is provided with a large rear access fitted with clam type doors which can be folded to an open position adjacent each side of the fuselage to further reduce the overall length in the folded configuration.
U.S. Pat. No. 3,327,969 to Head discloses an aircraft adapted for in-flight conversion from a helicopter type of flight to a conventional airplane type of flight, and vice versa.
U.S. Pat. No. 3,635,426 to Stanley discloses a rotary wing transport aircraft especially adapted for short haul transport service, having rotor blade jet devices providing torqueless rotor drive, outboard propulsive airscrews, and gas generators or gas turbine engines some of which provide for drive of the outboard airscrews and at least one of which provides hot effluent gas which is somewhat cooled by mixing with air or water and then fed to the rotor driving jet devices.
U.S. Pat. No. 3,520,497 to Schramm, discloses a frame work for a helicopter which is especially suitable for, but not limited to, a one-man helicopter which is tough, springy, light of weight, and able to absorb extraordinary loads with minimum damage to the structure and its occupant. The construction includes a minimum number of parts and is readily adapted to the use of bent steel tubing in a welded structure.
Each of the above prior art patents pertain to original modifications in the conventional design of aircraft to accomplish a specific, unique operation. None of the references deal with the process of taking a conventional, multi-passenger helicopter from a primary design use to a second, un-anticipated use after the primary function has ceased. In particular, the process of the invention utilizes conventional military and/or civilian helicopters, which have, for one reason or another been declared surplus and in many cases, scrapped, and produces a less complex, inexpensive, lighter weight, special purpose, helicopter. In a first embodiment, the invention converts the helicopter from a dual-piloted, multi-passenger aircraft to a helicopter gunship flown by a single operator/pilot. Other potential special uses include observation aircraft, fire fighting or emergency rescue.